This invention relates to the handling of solid materials, and particularly the handling of solid particulate materials where they are passed from a low pressure system to a higher pressure system. There are many processes in the petrochemical industry that use catalysts and adsorbents. The catalysts and adsorbents are frequently transferred between reaction units and regeneration units, and often there is a flow of the catalyst and/or adsorbent through the system comprising the reaction unit and the regeneration unit.
Currently, the transfer of catalyst between two vessels with reverse pressure gradient is achieved by using a valved lock hopper and flow control hopper, by valved lock hopper with a nuclear level detection instrument or by using a valveless hopper. The flow control and valved lock hopper is used to change the pressure and environment, in order to transfer the solid material from a lower pressure vessel to a higher pressure vessel. In a flow control and valved lock hopper, the flow control hopper and the valved lock hopper are separated. The flow control hopper is used to control the flow of solid particles and the valved lock hopper is used to change the pressure and environment, that is to raise the pressure for the solid particles to be transferred. In a valved lock hopper with a nuclear level detection instrument, the flow control and pressure change is combined into one gas tight valved lock hopper with nuclear level detection, the nuclear level detection is used to control the flow rate of solids by loading and unloading between the high and low level in a given time interval and the gas tight valved lock hopper changes the pressure and environment. With a valveless lock hopper, the flow control and pressure change is also combined into the lock hopper, where the hopper has three internal compartments. The pressure is cycled in the middle compartment with nuclear level detection and the solid particles are transferred from the top compartment to the middle compartment to the bottom compartment in a batchwise manner, when the pressure is equalized between the top and middle compartments and then the middle and bottom compartments The control of the solid flow rate is achieved by batchwise solid transfer between the high and low nuclear level detection for a given time interval.
Continuous nuclear level detection is typically used where most other technologies are unsuccessful. Different radioactive isotopes are used, based on the penetrating power needed to pass through a vessel and the material in the vessel. Radiation from the source is detected on the other side of the vessel. Its strength indicates the level of the material in the vessel. The devices are noninvasive, making them very useful for the dusty environments associated with solids handling. The level detection is affected by density changes as the vessel fills with solids.
Problems exist for the first two systems which add to maintenance and the loss of catalyst through grinding that creates fines, especially in the gas tight valves where the valves are completely closed in the solid and gas lines in the dusty environment and which eventually develop leaks. The valveless lock hopper loads and unloads the solids by changing the hydraulics which is sensitive toward the design of the vessel and the solid transfer pipe between the vessel. This can develop a phenomenon call “seal loss” which is when the reverse pressure in the solid transfer line is too high and blows the solids to empty the solid seal in the transfer pipe.